Switch perspective in a RCP application since Eclipse Juno?

In my RCP application I use this code to switch perspective :

IWorkbenchWindow window = getViewSite().getWorkbenchWindow();
window.getWorkbench().showPerspective(PRODUCT_PERSPECTIVE_ID, window);

I didn't change my code but I changed my developement environnement from

java 6 64bits + windows + Eclipse Indigo

to

java 7 32bits + windows + Eclipse Juno

And now the perspective doesn't switch any more, with no exception and nothing suspect visible in debug.

I didn't find any bug report.

Is there an explanation ? A workaround ?